ACPAtmospheric Chemistry and PhysicsACPAtmos. Chem. Phys.1680-7324Copernicus GmbHGöttingen, Germany10.5194/acp-13-1377-2013Air pollution and associated human mortality: the role of air pollutant emissions, climate change and methane concentration increases from the preindustrial period to presentFangY.15NaikV.2HorowitzL. W.3MauzerallD. L.141Program in Science, Technology and Environmental Policy, Woodrow Wilson School of Public and International Affairs, Princeton University, Princeton, NJ, 08544, USA2UCAR/Geophysical Fluid Dynamics Laboratory, Princeton, NJ, 08540, USA3NOAA Geophysical Fluid Dynamics Laboratory, Princeton, NJ, 08540, USA4Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ, 08544, USA5now at: Department of Global Ecology, Carnegie Institution for Science, Stanford, CA 94305, USA0402201313313771394This work is licensed under a Creative Commons Attribution 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0/This article is available from http://www.atmos-chem-phys.net/13/1377/2013/acp-13-1377-2013.htmlThe full text article is available as a PDF file from http://www.atmos-chem-phys.net/13/1377/2013/acp-13-1377-2013.pdf

Increases in surface ozone (O<sub>3</sub>) and fine particulate
matter (&le;2.5 μm aerodynamic diameter, PM<sub>2.5</sub>) are associated
with excess premature human mortalities. We estimate changes in surface
O<sub>3</sub> and PM<sub>2.5</sub> from pre-industrial (1860) to present (2000) and the
global present-day (2000) premature human mortalities associated
with these changes. We extend previous work to differentiate the
contribution of changes in three factors: emissions of short-lived air
pollutants, climate change, and increased methane (CH<sub>4</sub>) concentrations,
to air pollution levels and associated premature mortalities. We use a
coupled chemistry-climate model in conjunction with global population
distributions in 2000 to estimate exposure attributable to concentration
changes since 1860 from each factor. Attributable mortalities are estimated
using health impact functions of long-term relative risk estimates for
O<sub>3</sub> and PM<sub>2.5</sub> from the epidemiology literature. We find global mean
surface PM<sub>2.5</sub> and health-relevant O<sub>3</sub> (defined as the maximum
6-month mean of 1-h daily maximum O<sub>3</sub> in a year) have increased by
8 ± 0.16 μg m<sup>−3</sup> and 30 ± 0.16 ppbv (results reported as
annual average ±standard deviation of 10-yr model simulations),
respectively, over this industrial period as a result of combined changes in
emissions of air pollutants (EMIS), climate (CLIM) and CH<sub>4</sub>
concentrations (TCH4). EMIS, CLIM and TCH<sub>4</sub> cause global
population-weighted average PM<sub>2.5</sub> (O<sub>3</sub>) to change by
+7.5 ± 0.19 μg m<sup>−3</sup> (+25 ± 0.30 ppbv),
+0.4 ± 0.17 μg m<sup>−3</sup> (+0.5 ± 0.28 ppbv), and
0.04 ± 0.24 μg m<sup>−3</sup> (+4.3 ± 0.33 ppbv), respectively. Total global changes in
PM<sub>2.5</sub> are associated with 1.5 (95% confidence interval, CI, 1.2–1.8)
million cardiopulmonary mortalities and 95 (95% CI, 44–144) thousand lung
cancer mortalities annually and changes in O<sub>3</sub> are associated with 375
(95% CI, 129–592) thousand respiratory mortalities annually. Most air
pollution mortality is driven by changes in emissions of short-lived air
pollutants and their precursors (95% and 85% of mortalities from
PM<sub>2.5</sub> and O<sub>3</sub> respectively). However, changing climate and
increasing CH<sub>4</sub> concentrations also contribute to premature mortality
associated with air pollution globally (by up to 5% and 15%,
respectively). In some regions, the contribution of climate change and
increased CH<sub>4</sub> together are responsible for more than 20% of the
respiratory mortality associated with O<sub>3</sub> exposure. We find the
interaction between climate change and atmospheric chemistry has influenced
atmospheric composition and human mortality associated with industrial air
pollution. Our study highlights the benefits to air quality and human health
of CH<sub>4</sub> mitigation as a component of future air pollution control
policy.